Rotary engine oil tank vent

ABSTRACT

An end cover for normally covering the outboard end of an end housing in a rotary engine has a wall forming a cavity that is shielded from engine oil to provide an elevated quiet zone to which air is vented internally from the top of the engine&#39;&#39;s oil tank and thence into the engine&#39;&#39;s internal breathing system.

United States Patent Green et al.

[ Dec. 30, 1975 1 1 ROTARY ENGINE OIL TANK VENT 3,859,013 1 1975 Stevenson 123/801 x 3,8 27 61975 G 123 196R 175] Inventors: Raymmd Green, Norm/"6; Paul 3 822 i221 6/1975 Kgi j new 123/196 R D. Stevenson, Ann Arbor, both of Mich.

[73] Assignee: General Motors Corporation, Primary Exami'ferwimam Ffeeh Detroit, Mich Assistant Examiner-Leonard Sm1th Attorney, Agent, or Firm-Ronald L. Phillips [22] Filed: Oct. 29, 1974 [21] App]. No.: 518,574

[57 ABSTRACT [52] U.S. C1 123/196 R; 123/801; 184/65;

418/83 An end cover for normally covering the outboard end [5 Int- C1-2 t t of an end housing in a rotary engine has a wall form. [58] Field of Search 418/83, 88, 94; 123/801, i a Cavity h i hi ld d from engine oil to provide 196 196 6-16, an elevated quiet zone to which air is vented internally 106; 180/691 from the top of the engines oil tank and thence into the engines internal breathing system. [56] References Cited UNITED STATES PATENTS 2 Claims, 7 Drawing Figures 3,855,987 12/1974 Green et a1. 123/801 X a? k 1 f \Ik a 1 14*: t 2 w z;

US. Patent Dec. 30, 1975 Sheet 2 0f 3 3,929,117

US. Patent Dec. 30, 1975 Sheet 3 of 3 3,929,117

ROTARY ENGINE OIL TANK VENT This invention relates to a rotary engine oil tank vent and more particularly to such a vent that is provided in an elevated position internally of the engine by cooperation between an end housing and an end cover.

In rotary engines having an oil tank that is closed at its top except for a suction passage to the pump and a drain passage from the engine, the interior of the tank above the oil level may have to be vented other than just through the drain passage to assure adequate drainage thereto from the engine. One obvious solution is to attach an external vent tube to the top of the oil tank. However, this tube is subject to possible damage and leakage could then be external of the engine. Thus, substantial advantages can be gained if an additional oil tank vent can be provided internally of the engine particularly if this can be accomplished simply and economically and without substantially disturbing existing engine structure.

According to the present invention there is provided a rotary engine oil tank vent arrangement wherein an existing end cover that normally covers the outboard end of an end housing is modified so as to form with the end housing a quiet or undisturbed zone that is in an elevated position in the engine above the oil tank. The top of the oil tank is open to the engine drain and, in addition, is vented to this quiet zone through an annular passage formed about a suction pipe that delivers the oil in the tank to the engines oil pump. This quiet zone is shielded from any oil that normally collects close by in the end housing and the air vented from the oil tank and delivered thereto is directed from there into a passage that opens to the engines breathing system at a further elevated position. As a result, air in the oil tank is not restricted in its ability to get out and thus good drainage to the oil tank is assured and without external vent tubing and the like.

An object of the present invention is to provide a new and improved rotary engine oil tank vent.

Another object is to provide in a rotary engine an elevated internal quiet zone provided by simple modification of existing parts with air vented internally from the tank to the quiet zone and then directed by this quiet zone at a further elevated position in the engines internal breathing system.

These and other objects of the present invention will become more apparent from the following description and drawing in which:

FIG. I is a side elevational view with parts in section of a rotary engine having an oil tank with an air vent constructed according to the present invention.

FIG. 2 is an enlarged view taken along the line 2--2 in FIG. 1.

FIG. 3 is an exploded view of certain of the engine parts.

FIG. 4 is an enlarged view taken along the line 4'4 in FIG. I. 1

FIG. 5 is a view taken along the line 5-5 in FIG. 4.

FIG. 6 is a view taken along the line 6-6 in FIG. 4.

FIG. 7 is a view taken along the line 77 in FIG. 4.

Referring to FIGS. 1, 2 and 3, there is shown a tworotor rotary engine I0 with an oil tank 12 vented according to the present invention and as installed in a vehicle. The engine has an outer body comprising a pair of end housings 14 (front) and 16 (rear), a pair of rotor housings l7 and 18, and an intermediate housing 19 between the two rotor housings l7 and 18, all

clamped together by bolts 20. The engine housing encloses a pair of cavities 22 and 23 that are defined respectively by inwardly facing peripheral walls 24 and 26 of rotor housings l7 and I8 and opposed, spaced parallel end walls 28, 30 and 32, 34 of front end housing 14 and intermediate housing 19 and the latter housing and rear end housing 16. Each of the peripheral walls 24 and 26 is in the shape of a two-lobe epitrochoid or curve parallel thereto whose center line is indicated at 36. A crankshaft 42 extends through the cavities 22 and 23 and is rotatably supported in main bearings 44 and 45 which are fixed in stationary gears 46 and 47 that are bolted to the respective housings 14 and 16 as shown in FIG. 1, the crankshafts axis being coincident with the center line 36 which is parallel to the peripheral walls 24 and 26.

The crankshaft 42 is provided in the housing cavities 22 and 23 with eccentrics 50 and 52 on which hollow rotors 54 and 56 having bearings 57 and 58 are mounted for rotation about the eccentric centers 59 and 60, these centers being located 180 apart and spaced equal distances from the crankshaft axis 36. The rotors 54 and 56 have the same general shape of a triangle having respectively three faces 61 and 62 which are convex and face the peripheral walls 24 and 26 and cooperate therewith and with the end walls 28, 30 and 32, 34 to define three variable volume working chambers 67 and 68 that are spaced about and move with the respective rotors within the engine housing.

Near the rear end of crankshaft 42 outboard of stationary gear 47, a distributor drive gear 69 is secured thereto and the rear end housing 16 has an annular rearwardly extending-projection 70 about this gear. An annular end cover 71 is received about this end of the crankshaft and fits into the projection 70 to close off the center of the engine at this end, the end cover having a lip seal at its inner diameter that contacts the crankshaft and being retained at its outer diameter which is sealed by an O-ring by a tapered snap ring 73 that fits in a radially inwardly facing groove 74 in the end housing projection 70.

A fixed cyclic relation between each of the rotors and the crankshaft is obtained by gearing between each of the rotors and the housing. Referring to rotor 54, there is the stationay gear 46 which is fixed to the housing and is received about and is concentric with the crankshaft 42. The gear 46 meshes with an internal tooth gear 75 that is concentric with and formed on the outboard side of rotor 54. The gear 75 has 1 /2 times the number of teeth as the gear 46 with the result that this gearing enforces a fixed cyclic relation such that the crankshaft makes three complete revolutions for every one complete revolution of the rotor. Similarly, the other stationary gear 47 meshes with an internal tooth gear 76 on the other rotor 56 with their mesh at a location diametrically opposite that of gears 46 and 75. Thus, the chambers 67 and 68 move with the respective rotors 54 and 56 as they revolve about their axes while also revolving about the crankshaft axis with each chamber twice undergoing expansion and contraction during each rotor revolution.

Sealing of the working chambers such as the working chambers 67 is effected by three apex seals 77 each of which extends the width of the rotor and is mounted in an axially extending slot at one of the rotor apexes, six corner seals 78 each of which is mounted in a hole in one of the rotor sides near one of the rotor apexes, and 12 side seals 79 each of which is mounted in an arcuate 3 groove in one of the rotor sides with these seals arranged in pairs and extending adjacent one of the rotor faces between two of the corner seals with the corner seals each providing a sealing link between one apex seal and the adjacent ends of two pairs of side seals. The apex seals 77 are each spring biased radially outward to continuously engage the peripheral wall 24 and both the corner seals 78 and the side seals 79 in both rotor sides are spring biased axially outward to continuously engage the respective end walls 28 and 30. In addition, there is mounted in grooves in each rotor side inward of the side seals 79 a pair of spring biased circular oil seals 82 which are concentric with the rotor and sealingly engage the opposite end wall to prevent oil from reaching further outward. The rotor 56 carries a similar gas and oil seal arrangement.

A combustible air-fuel mixture is delivered by an induction system, not shown, that includes a carburetor that is mounted on an intake manifold. The intake manifold is connected to the engine housing and has branches that communicate in the engine housing with intake ports 84 and 86 in the respective housing end walls as shown in the end walls 30 and 34 in FIG. 3. Upon rotor rotation the combustible air-fuel mixture is sequentially, periodically admitted to the chambers 67 and 68 as they are expanding by the traversing motion of the rotor sides relative to the respective intake ports whereafter the chambers then close to their intake ports and contract to compress the thus trapped airfuel mixture in readiness for ignition. Combustion by spark ignition is provided by a suitable ignition system having a distributor driven by drive gear 69. The ignition system applies voltage at the proper time to pairs of spark plugs 88 and 90 which are mounted on the rotor housings, as shown in FIG. 3, with their electrodes open to the combustion chambers through the respective peripheral walls. For example, the electrodes of the two spark plugs 88 mounted on front rotor housing 17 are open to the chambers 67 through the interior peripheral wall 24 and are peripherally spaced thereabout so that one plug leads the other plug relative to rotor rotation. In such an arrangement both plugs are fired at the same time or different times or only one plug is fired according to certain engine operating conditions as is well known. With combustion the peripheral wall takes the reaction to force the rotor to continue rotating and eventually each working chamber following the power phase is exhausted during the exhaust phase by an exhaust port 92 in the peripheral wall 24 that is periodically traversed by the rotor apexes and is open to an exhaust manifold secured to the exterior of the engine housing.

Describing now the lubrication system but deferring the details of the oil tank and its vent until later, oil is drawn from the oil tank 12 by an oil pump 100 through a suction hole 102 in the bottom of the rear end housing 16 and thereafter passes forwardly to the front end housing 14 where the oil pump is mounted via a horizontal passage 104 formed in the housings 16, 18, 19, 17 and 14 as shown in FIG. 3. The oil pump 100 is of the internal-external gear type and is mounted about and is driven by the crankshaft 42 as best shown in FIG. 1. Oil pump 100 delivers the oil under pressure to an external cooler, not shown, from which the oil is then directed to a passage 106 in the rear housing shown in FIG. 3. Passage 106 delivers the oil to an oil filter 108 that is mounted on the rear end housing and from the filter, oil is delivered to a distribution passage 110 with the pressure feed to the cooler and also the distribution pressure in the engine controlled by suitable pressure regulator valves, not shown, such as disclosed in copending U.S. patent application Ser. No. 432,848, filed Jan. I4, 1974 and assigned to the assignee of this invention. The pressure distribution passage runs into an oil gallery tube 112, shown in FIG. 1, that passes through a passage in the top of the rotor housings l7 and 18 and intermediate housing 19. Tube ll2joins at its opposite ends in the front and rear end housings l4 and 16 with long drilled holes 114 and 116, respectively, that run from the gallery downward toward the center of the housings and stationary gears 46 and 47. Oil is forced into the crankshaft at each end through respective holes 118 and 120 in the front and rear stationary gears 46 and 47, radial holes 122 and 124 in the front and rear main bearings 44 and 45 and radial holes 126 and 128 in the crankshaft 42 to a long central feed hole 130 in the crankshaft that is drilled from the rear end thereof and then plugged by a press-fitted ball 132. Thus, the main bearings 44 and 45 are fed with oil for lubrication and, in addition, radial holes 134 and 136 connect the central feed passage 130 to feed oil to the rotor bearings 57 and 58 for their lubrication. In addition, radial orifices 138 and 140 connected to the central feed passage 130 direct oil radially outwardly between the phase gears 46, 75 and 47, 76 and eccentrics 50 and 52, respectively, to lubricate the phase gears and also to pass into the interior of the respective rotors 54 and 56 to effect their cooling. The rotors each have an internal web 142 with holes 144 to provide for circulation therethrough in an axial direction with the oil then exiting outwardly of the rotor and into cavities 146 and 148 in the front and intermediate housings 14 and 19 in the case of rotor 54 and into the intermediate housing cavity 148 and a cavity 150 in the rear end housing 16 in the case of rotor 56. Oil in the pressurized distribution passage 110 is also delivered to an oil metering pump, not shown, which meters oil at a suitable rate to lubricate the rotors gas seals. This oil metering pump may be of the type disclosed in copending U.S. patent application Ser. No. 357,072, filed May 3, 1973 and assigned to the assignee of this invention and may be connected to meter oil to mix with the fuel in the carburetor or to oil feed ports in the housing walls on which the seals slide.

The oil after leaving the main bearings, rotor bearings, phase gears and rotor cavities, falls through the cavities 146, 148 and 150 to a horizontal drain passage 158 that extends through the housings as shown in FIGS. 1 and 3. The oil then drains to the oil tank 12 through a drain-vent hole 160 in the rear housing 16 as best shown in FIGS. 2 and 3. Air is vented internally in the engine by a continuous air flow which is effected by the provision of a breather passage 162 in the front end housing 14 which is connected by a hose 164 to pull air from the engine's air cleaner and the provision of an air-oil separator 166 which is mounted on the rear housing 16 and is connected by a hose 168 and a PCV valve, not shown, to a vacuum zone in the carburetor. The separator 166 has a construction which is operative to permit air to be pulled from a top cavity 170 in the rear housing to the carburetor while separating out and draining oil to the drain cavity 150. In this internal air flow system there are three parallel air paths through the housings, namely the drain passage 158 which carries air along with the oil from the front end housing to the oil tank 12, an upper vent passage [72 that can carry air from either the front housing breather cavity 162 to the rear end housing vent cavity 170 or in the reverse direction to compensate for the air carried from the oil drain passage and a third passage which is through the hollow rotors. In addition, the upper vent passage, the rotor vent passage and the drain passage are connected in the front, intermediate and rear housings for cross-flow and pressure equilization as shown in FIGS. 1 and 3. These connecting passages in the front, intermediate and rear housings are provided with configurations 174 and deflectors 175 as shown on the intermediate and rear housings in FIG. 3 which act to prevent oil splash up into the vent passage 172 and to the air-oil separator 166. Furthermore, any combustion gas blowby from the rotors through the connecting passages in the front, intermediate and rear housings is thus free to move up to the vent passage 172 through the air-oil separator 166 and the PCV valve out to the carburetor.

The oil tank 12 which is vented internally of the engine in accordance with the present invention as described in detail later comprises a stamped sheet metal pan 180 that is formed to provide a deep reservoir which is generally rectangular in cross-section as best seen in FIG. 2 and is boot-shaped in a horizontal plane or plan view as best seen in FIG. 3, this bootshape providing the maximum volume in a certain confined space in the vehicle. A cover or top assembly fits into and over the pan 180 and comprises a screen and suction pipe subassembly 184, a stamped sheet metal inner cover 186 and a stamped sheet metal outer cover or top 188.

The screen and suction pipe subassembly 184 comprises three pan-shaped sheet metal stampings; namely, a bottom piece 190, a top piece 192 and an anti-drainback inner wall piece 194 as shown in FIG. 2. A screen 196 of suitable size mesh is arranged between the concave sides of the bottom 190 and the inner wall 194 and the concave side of the top 192 is deeper and arranged over the convex side of the inner wall. These sheet metal pieces have abutting peripheral flanges which are secured along their length by rolling over the bottom members flange which is extended for that purpose. These parts are elongated to extend almost the length of the tank and have a transverse extending projection 197 as shown in FIG. 2 to locate an intake hole 198 in the bottom of this projecting portion in the center of the oil pool. The intake hole 198 is elevated at a minimum height by bumps, not shown, that project upwardly from pan 180 and engage the bottom of subassembly 184. Oil after being drawn into theintake hole 198 passes through the screen 196 and then through a hole, not shown, in the inner wall 194 near the rear end thereof and then between the inner wall and the top 192 to the lower end of a vertical suction pipe 202 which projects through and is welded to a collar 204 formed on the top near the front end thereof. The 1 upper end of suction pipe 202 is received by the engines suction hole 102 and an O-ring 205 is provided to seal this connection as shown in FIGS. 2 and 4.

The screen and suction pipe assembly 184 is secured to the underneath side of the inner cover 186 by three straps 208 which at their lower end are welded to the underside of the bottom pieces flange and at their upper end are welded to the underside of the inner cover. The top side of the inner cover 186 has a pair of channels 210 and 212 formed therein and a remaining planar portion 214 which is sealed by a suitable scaling compound and then welded to the underside or ceiling of the outer cover 188. The channel 210 is relatively deep and wide and in cooperation with the ceiling of the outer cover 188 provides a longitudinal drain-vent passage 216. Passage 216 is open at one end to a drainvent hole 218 provided by a vertical tubular portion 220 which is formed on the top side of the outer cover 188 near the front end and fits closely in the engines drain-vent hole 160 with an O-ring 221 provided to seal this connection of the oil tank with the engine. The drain-vent passage 216 extends to the rear end of the inner cover 186 to open to the reservoir near the rear end thereof. A U-shaped vent passage 222 is provided by the other channel 212 which extends at one end as an annulus about a vertical tubular portion 223 which is formed on the top side of the inner cover 186 near the front end and projects with clearance up into a tubular portion 224 which is formed on top of the outer cover 188. The tubular portion 224 projects up into close fitting relationship with an enlarged portion 225 of the engines suction hole 102 as shown in FIG. 2. The suction pipe 202 extends up through tubular portions 223 and 224 to fit close in the engines suction hole 102 and these tubular parts are sized to leave an annular clearance between the tubular portions 223 and 224 of the inner and outer covers and also between the tubular portion 224 and suction pipe 202 and no clearance between the inner covers tubular portion 223 and the suction pipe so that there is sealing engagement between these latter two parts.

A vent hole 227 meets with the enlarged hole portion 225 above the outer covers tubular portion 224 as shown in FIGS. 2 and 4 and thus provides a vent access for the passage between suction pipe 202 and the outer covers tubular portion 224, there being provided an O-ring 228 to seal this connection of the oil tank with the engine. To assure good venting, it is required that the vent hole 227 be connected to the engine s internal breathing system via a quiet or undisturbed zone in an efficient manner. This is accomplished according to the present invention by simply forming a shield or wall 229 integral with the inboard side of end cover 71 that extends a substantial circumferential distance and then turns radially outward at its two ends 230 and 231 as shown in FIG. 4. The ends 230 and 231 are machined to have a close fit with the inner diameter of the end housing projection and are at different elevations. In addition, the wall 229 has an end face 232 which is forced tight against a flat on the rear end housing 16 outward of the stationary gear 47 with the snap ring 73 installed as shown in FIGS. 5 and 7. As a result, there isformed a cavity 234 of varying elevation within the oilsupplied annular cavity 235 in which the distributor drive gear 69 is located and it is to the lower end of cavity 234 that the vent hole 227 is connected near the wall end 230 as shown in FIGS. 4 and 7. The upper end of cavity 234 near wall end 231 is connected as shown in FIGS. 4 and 5 via a transverse vent hole 236 in the rear end housing 16 to an elevated portion of the drain cavity in this housing which is away from the path of oil drainage, the drain cavity being in turn open at its top to the top vent cavity 170. As shown in FIG. 6, the cavity 235 with the distributor drive gear 69 drains cavity 150 and the vent connection is thus well above this drainage. Thus, air is allowed to freely escape from the oil tank into the engines breathing system by the quiet or undisturbed zone 234 which is shielded by end cover wall 229 from any oil that collects behind stationrearward with a downward slope along the underneath side of the outer cover to a location near the rear end of the reservoir and then turns and extends forward still with a downward slope to a hole 240 at the center of the oil tank and above the normal oil level that occurs with shifting of the oil level during engine operation with the vehicle either accelerating, decelerating or turning. The channel 212 thereafter continues at a relatively constant depth to the front end of the inner cover where it opens to the reservoir.

The pan 180 has a peripheral flange which is welded to the underneath side of the outer cover 188 along its periphery and the oil tank is secured to the engine by means of four holes which extend through the pan 180 and outer cover 188 and receive bolts 242 as shown in FIGS. 1 and 3 with two of these bolts engaging the rear rotor housing 18 and the other two bolts engaging the rear end housing 16.

Describing now the oil flow to and from the oil tank 12 and the venting of the oil tank that is thus provided, oil is drawn through the suction hole 198 then through the screen 196 to the rearwardly located hole in the inner wall 194 whereafter it passes forward and then up through the suction pipe 202 to the engines lubrication system while an equal flow from the engines internal drain system drains to the engines drain-vent hole 160 where it then passes through the oil tank's drain-vent hole 218 and is conveyed in the oil tank by the drainvent passage 216 to replenish the oil reservoir. This returning oil carries with it a substantial amount of air trapped in the form of foam which must be removed from the closed oil tank to allow the oil to continue to return. This air is vented in part by making the drainvent connection as large as practical to allow air to back up through the same hole it came down. To overcome any impedance to the venting, air from the top of the tank is also allowed to vent through the vent passage 222 to vent hole 227 with the downward slope of this passage causing oil that is pulled in with the air to drain out through the hole 240. Vent air passes up through hole 227 to the elevated quiet zone 234 and from there out the hole 236 to an elevated zone in the engine's breathing system which has the air circulating to the engines intake. Since this oil tank vent connection is out of the way of draining oil, there is no tendency for it to clog with oil and therefore the air in the oil tank has unrestricted ability to get out and permit easy entry of the draining oil through drain-vent hole 218. It will also be appreciated that the drain hole 240 is located at the center of the tank and above the highest normal oil level so that this vent is always open to the interior of the oil tank above the oil level.

The above described embodiment is illustrative of the invention which may be modified within the scope of the appended claims.

We claim:

1. A rotary engine including a pair of end housings and a crankshaft rotatably supported in said end housings and an annular end cover received about said crankshaft normally covering an oil supplied cavity on the outboard side of one of said end housings, said one end housing having located underneath a drain-vent hole to which oil drains and through which air can be vented into the engine and also having located underneath a suction-vent hole through which oil can be supplied to the engines lubrication system and also through which air may be vented into the engine, an oil tank secured to said engine in an underneath location, said oil tank having a drain-vent hole sealingly connected to the drain-vent hole in said one end housing, said oil tank also having a suction-vent hole sealingly connected to the suction-vent hole in said one end housing, suction passage means extending from said oil tank through said suction-vent holes into said engine, vent passage means also extending from said oil tank through said suction-vent holes into said engine, said end cover having a wall cooperating with said end housing on the outboard side to provide a quiet zone shielded from said oil supplied cavity elevated above said oil tank, an upwardly extending elongated vent passage in said one end housing connecting said vent passage means to said quiet zone at a low location, and another vent passage in said one end housing connecting said quiet zone at a high location to the engine's internal breathing system at a place away from any oil drainage.

2. A rotary engine including a pair of end housings and a crankshaft rotatably supported in said end housings and an annular end cover received about said crankshaft normally covering an oil supplied cavity in an annular projection on the outboard side of one of said end housings, said one end housing having located underneath a drain-vent hole to which oil drains and through which air can be vented into the engine and also having located underneath a suction-vent hole through which oil can be supplied to the engines lubrication system and also through which air may be vented into the engine, an oil tank secured to said engine in an underneath location, said oil tank having a drain-vent hole sealingly connected to the drain-vent hole in said one end housing, said oil tank also having a suction-vent hole sealingly connected to the suctionvent hole in said one end housing, suction passage means extending from said oil tank through said suction-vent holes into said engine, said suction passage means and said oil tank around said oil tank suctionvent hole providing an annular vent passage about said suction passage means open to said oil tank, said end cover having an inwardly extending wall with a circumferentially extending face engaging the outboard side of said end housing and radially outwardly extending ends extending to said annular projection to provide a quiet zone shielded from said oil supplied cavity elevated above said oil tank, an upwardly extending elongated vent passage in said one end housing connecting said vent passage to said quiet zone at a low location, and another vent passage in said one end housing connecting said quiet zone at a high location and in a transverse direction to the engine's internal breathing system at a place away from any oil drainage.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,929,117

DATED December 30, 1975 |N\/ ENTOR(S) Raymond J. Green, Paul D. Stevenson it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: 0

Column 2, line 45, "stationry" should read stationary Column 6, line 63, after "drains" insert to drain Signed and Sealed this Fourteenth Day Of September 1976 [SEAL] Arrest:

RUTH c. MASON c. MARSHALL DANN Arresting Officer Commissioner oj'larents and Trademarks 

1. A rotary engine including a pair of end housings and a crankshaft rotatably supported in said end housings and an annular end cover received about said crankshaft normally covering an oil supplied cavity on the outboard side of one of said end housings, said one end housing having located underneath a drain-vent hole to which oil drains and through which air can be vented into the engine and also having located underneath a suction-vent hole through which oil can be supplied to the engine''s lubrication system and also through which air may be vented into the engine, an oil tank secured to said engine in an underneath location, said oil tank having a drain-vent hole sealingly connected to the drain-vent hole in said one end housing, said oil tank also having a suction-vent hole sealingly connected to the suction-vent hole in said one end housing, suction passage means extending from said oil tank through said suction-vent holes into said engine, vent passage means also extending from said oil tank through said suction-vent holes into said engine, said end cover having a wall cooperating with said end housing on the outboard side to provide a quiet zone shielded from said oil supplied cavity elevated above said oil tank, an upwardly extending elongated vent passage in said one end housing connecting said vent passage means to said quiet zone at a low location, and another vent passage in said one end housing connecting said quiet zone at a high location to the engine''s internal breathing system at a place away from any oil drainage.
 2. A rotary engine including a pair of end housings and a crankshaft rotatably supported in said end housings and an annular end cover received about said crankshaft normally covering an oil supplied cavity in an annular projection on the outboard side of one of said end housings, said one end housing having located underneath a drain-vent hole to which oil drains and through which air can be vented into the engine and also having located underneath a suction-vent hole through which oil can be supplied to the engine''s lubrication system and also through which air may be vented into The engine, an oil tank secured to said engine in an underneath location, said oil tank having a drain-vent hole sealingly connected to the drain-vent hole in said one end housing, said oil tank also having a suction-vent hole sealingly connected to the suction-vent hole in said one end housing, suction passage means extending from said oil tank through said suction-vent holes into said engine, said suction passage means and said oil tank around said oil tank suction-vent hole providing an annular vent passage about said suction passage means open to said oil tank, said end cover having an inwardly extending wall with a circumferentially extending face engaging the outboard side of said end housing and radially outwardly extending ends extending to said annular projection to provide a quiet zone shielded from said oil supplied cavity elevated above said oil tank, an upwardly extending elongated vent passage in said one end housing connecting said vent passage to said quiet zone at a low location, and another vent passage in said one end housing connecting said quiet zone at a high location and in a transverse direction to the engine''s internal breathing system at a place away from any oil drainage. 